Method of recovering mineral values from ore



Jan. 26, 1960 D. H. FENSKE 2,922,522

METHOD OF' RECOVERING MINERAL VALUES FROM ORE Filed June 28, 1957 fa/oezz @fm MAL@ METHOD F RECOVERING MINERAL VALUES FROM ORE Douglas H.Fenske, Lakeland, Fla., assignor torlnternanational Minerals & ChemicalCorporation, a corporation of New York Application June 28, 1957, SerialNo. 668,620

7 Claims. (Cl. 209-166) This invention relates to the recovery ofphosphate and other mineral constituents from ores containing the same.More particularly, the invention relates to the recovery of phosphateand metallic minerals such as ilmenite, rutile, zircon, monazite and thelike. Still more particularly, it relates to the recovery of anappreciable amount of the phosphate normally lost in the general milltails.

Phosphate ore from the central district of Florida is subjected tootation operations to produce high grade phosphate concentrates. Theflotation procedure usually involves a rougher flotation operationwhereby the phosphate is iloated utilizing anionic reagents such asfatty acids. Phosphate intermediate concentrate is upgraded to a nalconcentrate of a grade between about 72% and 78% BPL by flotation withcationic reagents such as long chain aliphatic amine acid additionsalts. The froth product from the amine flotation is a predominantlysilica product containing from about 8 to 20% BPL product which inso-called open circuit operation is discharged to waste and in closedcircuit carries so much material such as heavy minerals that the circuitperiodically must be purged Iwith consequent losses.

It is an object of this invention to overcome the shortcomings anddisadvantages of processes heretofore in use.

It is another object of the invention to provide a process wherein anappreciable portion of the phosphate formerly discharged to waste in thesilica tailings is recovered.

It is still another object of the invention to provide an improvedprocess permitting recovery of the heavy minerals as a bulk concentrate.

It is a further object of the invention to provide a relativelyinexpensive method of preferentially depressing silica in a phosphateflotation operation following amine llotation.

It is still a further object of the invention to provide a method forrendering amine ilotation agents ineffective in subsequent flotationoperations on the products of amine llotation.

Now it has been discovered that, for example, the froth overow product,containing phosphate and heavy minerals and predominatng in silica,obtained by flotation of nitrogenous positive ion reagent treatedphosphate concentrate can be subjected to a further yflotation operationwithout addition of flotation reagents but in the presence of controlledamounts of halogen oxidizing agents to ellectively separate silica,leaving a predominantly phosphate-heavy minerals fraction from whichboth components can be recovered.

The appended drawing is a llowsheet showing the method of the presentinvention as an improvement on the prior art method of concentratingphosphatic ores by anionic ilotation to produce a rougher phosphateconcentrate, followed by cationic flotation of the concentrate.

In this new and novel process, t'he predominantly silica frothoverflowing the nitrogenous positive ion reagent *l duction into theflotation cells.

2,922,522 Patented Jani. 26, 196.0

or amine reagent flotation cell is accumulated in va sump or passeddirectly to a flotation cell. To 'the froth'prod? uct in the sump or inthe cell is added between about 0.05 pound of halogen and about 1.5pounds of halogen per ton of reagentized solids to be subjected toagitation and aeration in the flotation operation with about 0.3 poundto about 1.0 pound preferred.

Halogen may be added in the form of gaseous chlorine or gaseous brominein the form of solution Vsuch as diluting water containing halogen insolution o'r sodium rock are segregated from material which isapproximately -j-l mm. size. The -1 mm. size -material is subjected tofurther washing for complete desliming, which des1iming is produced byseparating the -150 mesh size material from the +150 mesh size material.The +150 mesh size material called sand is subjected to aV screeningoperation to produce a +35 mesh size fraction which is passed to spiralfor concentration and a -35 mesh size fraction which is the feed to theflotation circuit. The major portion of the heavy mineral in thisphosphate material reports in this -35 +150 mesh size fraction.

In the phosphate flotation operation, the 35 mesh fraction of the ore ismixed with anionic reagents which have an ainity forY phosphate materialand the heavy minerals. The reagentized mixture is subjected tollotation under conditions giving high recovery and selectivitypermitting production of a throw-away silica tail product.

Anionic or carboxyl containing negative ion agents which are useful inthe first or rougher stage of phosphatev concentration are for example,the higher fatty acids, i.e., oleic, linoleic, and abietic acids,natural resin acid, tall oil, naphthenic acids, alkyl sulphonated fattyacids, acid esters of high molecular weight aliphatic alcoholsand thesoaps of such materials. Included within the term soaps of such negativeion or anionic type reagents, are the alkali metal and alkaline earthmetal soaps.

such as sodium, potassium, aluminum, calcium and magnesium soaps. Soapsmay also be formed by reacting suchv reagents with ammonia or aqueoussolutions thereof. The metallic mineral-containing ore and phosphatehaving a -35 mesh particle size, is reagentized with one orY more ofthese reagents in; the presence of water by agitating thernixture at asolids content between about 50% and about 75% by weight, followingwhich the slurry is diluted to a concentration suitable for intro- Inthese cells a froth is formed which carries the phosphate and heavymineral to the top where this fraction is removed by overllow. This oreproduct, overflowing from the* anionic flotation cell, is recovered forfurther processing as follows: The anionic reagents areremoved from thesolids by scrubbing withy sulfuric acid. After scrubbing,vthe solids arewashed fr'ee of reagents and` acid by agitation with wash water. Thewashed solids are then reagentized with a cationic flotation reagentdesigned to remove the minor compoy nent of the concentrate, i.e.,silica, and the heavy mineral. Useful cationic or positive ion reagents:for thissalts with mineral and organic acids, esters of aminoY alcoholwith higher molecular weight fatty acids, and higher alkyl substitutedisoureas and their water-soluble salts, alkylsubstituted pyridinium andquinolinium watersoluble salts and the like. i v i Oneof theproducts ofthis cationic 'dot-ation operation is a final phosphate concentratewhich is the underflow from thefotation cells. The froth overflow fromthe cationic flotation is al mixture of silica, phosphate, and heavyminerals. A

The froth mixture or slurry which usually contains between about 20%4and about 30% of solids is generally accumulated in a sump, slurriedwith water to form a pulp containing about 10 to l25% by weight ofsolids and for example, ysodium hypochlorite solution of A% strength isadded at a rate of about 0.5 to 2.0- pounds per ton of froth mixture.From this sump the slurry is pumped directly to a dotation cell of theFagergren, Denver, or similar type for agitation and aeration. Theunderilowv product from this ilo-tation operation is predominantlysilica whose phosphate content is about 3;?, to l that of the froth ofthe cationic otation running about 2 to 8 BPL and 0.2% to 2.0% heavyminerals as against to about 25% BPL and 3% to 5% heavy minerals in thefroth feed.

"Phosphate-heavy mineral froth overflowing the cell generally willcontain 30 to 50% BPL and 5 to 15% heavy minerals and will requirescrubbing treatment such as washing with sulfuric acid before subsequentprocessing to separate phosphates 4and heavy minerals unless the frothis to be recycled for mixing with feed to the rougher flotationoperation. Generally, the phosphate-heavy minerals fraction isVde-reagentized and subjected to gravity separation operations either inspirals or on tables or the like. The heavy mineral fraction separatedin this manner will usually be a bulk concentrate containing about 85 to95% of heavy minerals. Phosphate fraction recovered in the gravityseparation is usually of the order of 38% to about 55% BPL which can berecycled to the positive ion yagent flotation where a nal phosphateconcentrate is being produced and permitting recovery of 50% to 75%formerly lost in the general mill tail..

When feeding through this process a 35 mesh phosphate feed ofapproximately 31.1% BPL, .4% heavy minerals, at a rate of 600 parts byweight per hour, a separation is made in the rougher flotation cellswhich produces a phosphate concentrate assaying about 68% BPL and 1.0%heavy mineralscontaining about 250 parts by weight of the feed. Thethrow-away tail fraction consists of about 350 parts by weight of thefeed and assays 93% silica and about 5% BPL.

The phosphate concentrate is separated in the amine otation cell torecover a concentrate containing about 180 parts by weight per hour anda froth otation product containing about. 70 parts by weight per'hour.The concentrate from the amine otation will assay about 77% BPL and theamine froth product will assay 76.3% silica, 14.5% BPL and 5.0% heavymineral.

The invention will be more fully understood from a study of thefollowing example which is given'by way of illustrationof the preferredembodiment of the in vention, and without any intention that theinvention be limited thereto.

xample A phosphate rock of the type found in phosphate pebble fields ofFlorida is subjected to a washing oper-ation in order to remove slimesand other organic matter. washed rock in an aqueous pulp is subjected toa screening'orhydraulic sizing operation whereby the larger particles ofrock are segregated from material which is approximately -35 meshstandard screen size. The latter material is then reagentized in anaqueous pulp containing about 70% solids with about one pound of areagent comprising about 88% tall oil and4 about 12% kerosene per ton ofore treated. About 2 to 4 pounds The of yfuel oil is added andsuflicient caustic soda` is mixed into the vmixture to give the latter apH of about 8 to 9. The resultant pulp is then subjected to a notationoperation at -a solids content of about 25 to 40% by Weight in aFagergren machine and a float product is recovered containingapproximately 60% tricalcium phosphate, about 20% silica, and about 1.0%of metallic numeral. This phosphatic product is then treated with about5 pounds per ton of solids of `sulfuric acid (60 B.) in order to removethe reagents therefrom. The acid-treated product is washed until itissubstantially neutral and is then reagentized in an aqueous pulpwithpa mixture of I long-chain aliphatic amine, the latter comprising amixture of about 73% of monooctadecyl amine'and about acid additionsalt.

VThe amine iioat product was conducted directly to a' Denver flotationcell and 24.2 pounds of sodium hyv pochlorite solution'was added per tonof feed solids as a solution containing .042 pound/ gallon of chlorineand introducing halogen in an amount corresponding 0.47 pound ofchlorine per ton of feed solids.

`Results of this flotation was as follows:

Percent Percent I Percent BPL Insol. PLM.

14. 54 81. 3 4. 98 5. 85 02. 5 2. 34 Concentrate 45. 56 41. 4 14, 39,

Concentrate from this otation, corresponding to about 13 parts by weightper hour,'was scrubbed with 2 pounds of sulfuric acid (60 B.) for 3minutes and the concentrate washed to neutrality. solids vflowing at therate of 1 ton of solidpper hour, a

separation was made as follows:

Percent Percent- Percent BPL 0l. H.M.

Fee 45.6 41.4 14.4 Heavy Mineral Tail 52. 9 32. 0 2. 2 Heavy MineralConcentrate 12. 1 84. 5 70. 0

.Having thus' described this invention, what is desired to be secured byLettersV Patent is:

l. In a dotation process wherein a phosphate ore-containing silica andheavy minerals is subjected to anionic dotation to separate a floatconcentrate comprising silica and,y heavy minerals and predominating inlphosphate, and the said anionic concentrate is subjected to cationicflotation to separate a float concentrate containing phosphate and heavyvminerals and predominating in silica,

, the steps which comprise adding to said cationic float concentrate ahalogen substance selected'from the group consisting of chlorine,brornne, hypochlorites, hypobromites and mixtures thereof in aproportion equivalent to between about 0.05 and about'l.5 pounds ofhalogen per ton of solids, and subjecting said cationic oat concentrateto further ilotation without further reagentizing to separate a floatconcentrate comprising predominately phosphate and heavy minerals.

2. The process of claim 1 wherein the proportion of v said'halogensubstance added to said cationic float concentrate is equivalent tobetween about 0.3 .pound and about 1.0'pound of halogen per ton ofsolids.

In a spiral separation, the

3. The process of claim 1 wherein said halogen substance is chlorine.

4. The process of claim l wherein said halogen substance is added in theform of sodium hypochlorite, the proportion of sodium hypochlorite beingbetween about 0.5 pound and about 2 pounds per ton of solids.

5. The process of claim 1 wherein said oat concentrate comprisingpredominately phosphate and heavy minerals is admiXed with suflicientacid to remove flotation reagents therefrom, and the dereagentizedsolids are subjected to gravity separation, whereby a phosphateconcentrate and a heavy minerals concentrate are separately recovered.

6. The process of claim 5 wherein said phosphate concentrate recoveredfrom said gravity separation is recycled to said cationic flotation.

7. In a otation process wherein a phosphate' ore containing silica andheavy minerals is subjected to anionic flotation with a fatty acid toseparate a oat concentrate comprising silica and heavy minerals andpredominating in phosphate, and the said anionic concentrate issubjected to cationic otation with a long chain aliphatic amine acidaddition salt to separate a float concentrate containing phosphate andheavy minerals and predominatng in silica, the steps which compriseadding to said cationic float concentrate between about 0.5 pound andabout 2 pounds of sodium hypochlorite per ton of solids, and subjectingsaid cationic oat concentrate to further flotation without furtherreagentizing to separate a float concentrate comprising predominatelyphosphate and heavy minerals.

References Cited in the file of this patent UNITED STATES PATENTS1,893,517 Gaudin Jan. 10, 1933 2,195,724 Gaudin et al. Apr. 2, 19402,753,997 Duke et al. July 10, 1956 OTHER REFERENCES Engineering andMining Journal, vol. 151, issue 8, pages 87, 88, 89, August 1950.

1. IN A FLOTATION PROCESS WHEREIN A PHOSPHATE ORE CONTAINING SILICA ANDHEAVY MINERALS IS SUBJECTED TO ANIONIC FLOTATION TO SEPARATE A FLOATCONCENTRATE COMPRISING SILICA AND HEAVY MINERALS AND PREDOMINATING INPHOSPHATE, AND THE SAID ANIONIC CONCENTRATE IS SUBJECTED TO CATIONICFLOTATION TO SEPARATE A FLOAT CONCENTRATE CONTAINING PHOSPHATE AND HEAVYMINERALS AND PREDOMINATING IN SILICA, THE STEPS WHICH COMPRISING ADDINGTO SAID CATIONIC FLOAT CONCENTRATE A HALOGEN SUBSTANCE SELECTED FROM THEGROUP CONSISTING OF CHLORINE, BROMINE, HYPOCHLORITES, HYPOBROMITES ANDMIXTURES THEREOF IN A PROPORTION EQUIVALENT TO BETWEEN ABOUT 0.05 ANDABOUT 1.5 POUNDS OF HALOGEN PER TON OF SOLIDS, AND SUBJECTING SAIDCATIONIC FLOAT CONCENTRATE TO FURTHER FLOTATION WITHOUT FURTHERREAGENTIZING TO SEPARATE A FLOAT CONCENTRATE COMPRISING PREDOMINATELYPHOSPHATE AND HEAVY MINERALS.